Nonvolatile semiconductor memory

Abstract

A memory cell array has a unit formed from one memory cell and two select transistors sandwiching the memory cell. One block has one control gate line. Memory cells connected to one control gate line form one page. A sense amplifier having a latch function is connected to a bit line. In a data change operation, data of memory cells of one page are read to the sense amplifiers. After data are superscribed on data in the sense amplifiers, and a page erase is performed, data in the sense amplifiers are programmed in the memory cells of one page. Superscription of data in the sense amplifiers allows a data change operation for byte data or page data.

1. A nonvolatile semiconductor memory comprising:
 a memory cell unit having a memory cell and first and second select transistors sandwiching the memory cell, wherein the memory cell and the first and second select transistors are connected in series and the memory cell has a stacked gate structure having a floating gate and a control gate; 
 a bit line connected to the first select transistor; 
 a cell source line connected to a source of the second select transistor; 
 a select gate line connected to a gate of the second select transistor; and 
 a control circuit which controls a program operation, wherein when the program operation is executed on the memory cell, the cell source line is set to have a first potential and the select gate line is set to have a second potential less than the first potential. 
 
     
     
       2. The nonvolatile semiconductor memory according to  claim 1 ,
 wherein the first potential is a power supply potential and the second potential is 0 V. 
 
     
     
       3. The nonvolatile semiconductor memory according to  claim 1 ,
 wherein each of the first and second select transistors has the same structure as the memory cell. 
 
     
     
       4. The nonvolatile semiconductor memory according to  claim 1 ,
 wherein one of byte data, page data and NAND block data is written to the memory cell array when the program operation is executed.